In dental treatment, it is well known to replace a missing tooth by an endosseous dental implant with an artificial crown. Typically, screw-shaped dental implants are used, such as the ones described by Brånemark in WO 97/49351. In order to anchor the implant in a patient's jaw-bone, a suitable drill hole is applied to the bone and the dental implant is fixed therein.
When the drill hole is applied to the jaw-bone, it is very important that the position, depth, width, and orientation of the drill hole are accurately adjusted to the patient's dental and osseous anatomy. A faulty drilling trajectory is very difficult to correct and can cause damage to nearby structures, such as the inferior alveolar nerve; it can also cause pain to the patient and, in some cases, even implant failure. In order to avoid deviations from the optimal drilling position and orientation, it is known to use a custom-made surgical template having an exact mating region in the mouth of the patient (either on the jaw-bone, the gums or the remaining teeth), which has bore tubes with the predetermined positions and orientations. Into these bore tubes, drill sleeves are inserted, which serve to guide the drills used for creating the implant drill holes in the jaw of the patient. Such a template with drill sleeves is described in U.S. Pat. No. 5,015,183, WO 2006/041430, and WO 97/43981, for example.
The drill sleeves are typically of hollow cylindrical shape and made of metal. During the drilling process, the drill sleeve's circular inner surface serves as guidance for the drill. To this end, it is known to place a secondary guiding element inside the drill sleeve, such as a drill spoon or a guiding cylinder, which can be exchanged in the course of the drilling process. The use of a drill sleeve in combination with a secondary guiding element is described in WO 2006/130067 or DE 10 2005 023 028, for instance. This approach is particularly favorable if several drills of increasing diameters are used for preparing the drill hole. Accordingly, several secondary guiding elements may be placed, one after the other, inside the same drill sleeve, each corresponding to a certain drill diameter. Alternatively, it is also possible that the drill is guided directly by the drill sleeve itself.
For applying the drill hole to the patient's jaw-bone, the dental drill is inserted into the drill sleeve, optionally containing a secondary guiding element, and then the hole is drilled in the axial direction of the drill sleeve. If the space above the implantation area is limited, especially in the case where a back tooth has to be replaced, it may be difficult to insert the drill axially into the drill sleeve. In order to overcome this problem, drill sleeves having a longitudinal slit have been described in WO 2007/104842. With these slitted drill sleeves, it is possible to insert the drill sideways, which considerably facilitates the insertion of the drill into the drill sleeve.
If, however, the space in the implantation area is limited in the lateral direction, especially if several adjacent implants are to be placed within the same tooth gap, there may not be enough space to place all drills sleeves necessary within the gap. In addition, if two adjacent drill sleeves placed into the template are at close quarters, the remaining template between the bore tubes for the drill sleeves may break. Accurate drilling of the drill hole can thus no longer be guaranteed.
It would therefore by desirable to provide a means for guiding a dental drill, which is suitable for use in implantation areas with laterally limited space.